Government labs, ships and aircraft carry data or information which is intended to be kept secret. Very often, this information is stored on magnetic hard disk drives (HDD) in computer-controlled equipment. Standard operating procedures in such environments often specify that the computer equipment or the hard disk drive be destroyed, or at least that the hard drive be erased, in the event that custody of the equipment, ship or aircraft may be lost. Such loss might be due to hostile action, or to mechanical failure or adverse environmental conditions.
One way that the information or data on a hard disk can nominally be erased is to use the “delete” function available in many operating systems. This function operates almost instantaneously. Unfortunately, the delete function does not actually delete the data involved, but instead it merely makes the region in which the data is stored on the magnetic data storage disk or platter available to be overwritten by new data. Simple techniques can undelete the information, so long as it has not been overwritten, and make it available. Thus, the delete function does not provide satisfactory security. It has been suggested that emptying the “recycle” bin following deletion of files will permanently remove the files so treated, but the data still remains on the magnetic data storage disk.
Another software solution is to perform a low-level format to thereby nominally erase the data on the hard disk. The low-level format essentially scans the disk with a head producing a magnetic field sufficient to reset the state of each bit of the disk. In this regard, the hard disk may be likened to a palimpsest, in that the recording medium may be reused after the erasure. With a palimpsest, some or all of the erased data may be recovered by sophisticated scientific techniques. It is well known that unless the format function is repeated several times, enough residual magnetization may remain on the disk from the data so that sophisticated electronic techniques can recover some or all of the data, as described, for example, in Secure Deletion of Data from Magnetic and Solid-State Memory, published by Peter Gutman of the Department of Computer Science at University of Aukland. Thus, complete erasure of data by formatting may not be fully effective. In addition, the formatting function is performed by scanning the read/write head along all the magnetic tracks on the magnetic data storage disk. The time required for these scans can be considerable, especially for large-capacity hard disk drives.
An industry has grown up providing degaussing services and degaussing equipment for erasing hard disk drives (HDD). The degaussing equipment is in the form of a device which generates a strong magnetic field and includes an enclosure into which a hard disk drive can be introduced for erasure. When activated, this device generates a magnetic field sufficiently strong to penetrate the chassis and/or housing of the hard disk drive and erase the disk in a time of a few minutes. While effective, the hard disk drive must be separated from the equipment in which it is normally housed and carried to the erasing device, which is likely to take excessive time in an emergency situation or on a vehicle subject to an attack. The size of the degaussing apparatus is relatively large, and the field strength required is such that a large power supply is used. Thus, a permanent installation is desirable for such equipment. In addition, erasure by this apparatus may render the hard disk drive unusable, which may be disadvantageous for situations in which emergencies may appear to be imminent but do not actually materialize.
Improved data erasing or erasure arrangements are desired.